p–d Orbital Hybridization in Ag‐based Electrocatalysts for Enhanced Nitrate‐to‐Ammonia Conversion

Abstract

Abstract Considering the substantial role of ammonia, developing highly efficient electrocatalysts for nitrate‐to‐ammonia conversion has attracted increasing interest. Herein, we proposed a feasible strategy of p–d orbital hybridization via doping p‐block metals in an Ag host, which drastically promotes the performance of nitrate adsorption and disassociation. Typically, a Sn‐doped Ag catalyst (SnAg) delivers a maximum Faradaic efficiency (FE) of 95.5±1.85 % for NH 3 at −0.4 V vs. RHE and reaches the highest NH 3 yield rate to 482.3±14.1 mg h −1 mg cat. −1 . In a flow cell, the SnAg catalyst achieves a FE of 90.2 % at an ampere‐level current density of 1.1 A cm −2 with an NH 3 yield of 78.6 mg h −1 cm −2 , during which NH 3 can be further extracted to prepare struvite as high‐quality fertilizer. A mechanistic study reveals that a strong p–d orbital hybridization effect in SnAg is beneficial for nitrite deoxygenation, a rate‐determining step for NH 3 synthesis, which as a general principle, can be further extended to Bi‐ and In‐doped Ag catalysts. Moreover, when integrated into a Zn‐nitrate battery, such a SnAg cathode contributes to a superior energy density of 639 Wh L −1 , high power density of 18.1 mW cm −2 , and continuous NH 3 production.